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Solar energy

Solar energy is the conversion of sunlight into usable energy forms. Solar photovoltaics (PV), solar thermal electricity and solar heating and cooling are well established solar technologies.

Solar photovoltaics

Solar photovoltaic (PV) systems directly convert solar energy into electricity. Solar PV combines two advantages. On the one hand, module manufacturing can be done in large plants, which allows for economies of scale. On the other hand, PV is a very modular technology. It can be deployed in very small quantities at a time. This quality allows for a wide range of applications. Systems can be very small, such as in calculators or off-grid applications, up to utility-scale power generation facilities.

In 2017, cumulative solar PV capacity reached almost 398 GW and generated over 460 TWh, representing around 2% of global power output. Utility-scale projects account for just over 60% of total PV installed capacity, with the rest in distributed applications (residential, commercial and off-grid). Over the next five years, solar PV is expected to lead renewable electricity capacity growth, expanding by almost 580 GW under the Renewables 2018 main case.

As PV generates power from sunlight, power output is limited to times when the sun is shining. However, as the IEA’s analysis on the system integration of variable renewable renewables has highlighted, a number of options (demand response, flexible generation, grid infrastructure, storage) exist to cost-effectively deal with this challenge.

Concentrating solar power

Concentrating solar power (CSP) devices concentrate energy from the sun’s rays to heat a receiver to high temperatures. This heat is then transformed into electricity – solar thermal electricity (STE).

From a system perspective, STE offers significant advantages over PV, mostly because of its built-in thermal storage capabilities. CSP plants can continue to produce electricity even when clouds block the sun, or after sundown or in early morning when power demand steps up. Both technologies, while being competitors on some projects, are ultimately complementary.

The deployment of CSP plants is at a stage of market introduction and expansion. In 2016, the installed capacity of CSP worldwide was 4.8 GW, compared to 300 GW of solar PV capacity. CSP capacity is expected to double by 2022 and reach 10 GW with almost all new capacity incorporating storage. CSP with storage can increase the flexibility of an energy system, facilitating the integration of variable renewable technologies such as solar PV and wind.

Solar heating and cooling

Solar thermal technologies can produce heat for hot water, space heating and industrial processes, with systems ranging from small residential scale to very large community and industrial scale. The required temperature to meet the heat demand determines the collector type and design.

The cumulative installed capacity of solar thermal installations reached an estimated 472 GWth by the end of 2017. However, the market continued to slow in 2017 for the fourth year in a row, as total annual installations decreased by 9% owing mainly to a continual slowdown in China.

To 2022, solar thermal heat consumption is expected to grow by over one-third, with installations in the buildings sector driving most of the increase. In the growing global market for cooling, there is also a huge potential for cooling systems that use solar thermal energy. By the end of 2015, an estimated 1,350 solar cooling systems were in operation globally.

Technology Roadmaps

The IEA has developed and regularly updates a series of global, low-carbon energy technology roadmaps which identify priority actions for governments, industry, financial partners and civil society that will advance technology development and uptake to achieve international climate change goals.

Technology Roadmap: Solar Photovoltaic Energy

Published: 15 September 2014

Solar energy is widely available throughout the world and can contribute to reduced dependence on energy imports. As it entails no fuel price risk or constraints, it also improves security of supply. Solar power enhances energy diversity and hedges against price volatility of fossil fuels, thus stabilising costs of electricity generation in the long term.

Solar PV entails no greenhouse gas (GHG) emissions during operation and does not emit other pollutants (such as oxides of sulphur and nitrogen); additionally, it consumes no or little water. As local air pollution and extensive use of fresh water for cooling of thermal power plants are becoming serious concerns in hot or dry regions, these benefits of solar PV become increasingly important.

Moreover, they can store thermal energy for later conversion to electricity. CSP plants can also be equipped with backup from fossil fuels delivering additional heat to the system. When combined with thermal storage capacity of several hours of full-capacity generation, CSP plants can continue to produce electricity even when clouds block the sun, or after sundown or in early morning when power demand steps up.

Technology Roadmap: Solar Heating and Cooling

Published: 9 July 2012

The solar heating and cooling (SHC) roadmap outlines a pathway for solar energy to supply almost one sixth (16.5 EJ) of the world’s total energy use for both heating and cooling by 2050. This would save some 800 megatonnes of carbon dioxide (CO2) emissions per year; more than the total CO2 emissions in Germany in 2009.

While solar heating and cooling today makes a modest contribution to world energy demand, the roadmap envisages that if concerted action is taken by governments and industry, solar energy could annually produce more than 16% of total final energy use for low temperature heat and nearly 17% for cooling. Given that global energy demand for heat represents almost half of the world’s final energy use – more than the combined global demand for electricity and transport – solar heat can make a significant contribution in both tackling climate change and strengthening energy security.

Technology Collaboration Programmes (TCPs)

Photovoltaic Power Systems TCP

The aim of the IEA TCP on Photovoltaics is to enhance the international collaborative efforts that facilitate the role of photovoltaic solar energy as a cornerstone in the transition to sustainable energy systems. This contributes to the cost reduction of PV power applications; increases awareness of the potential and value of PV power systems; fosters the removal of both technical and non-technical barriers; and enhances technology co-operation. There are currently 24 Contracting Parties, including China, Israel, Malaysia and Mexico, and four Sponsors.

Solar Heating and Cooling TCP

The aims of the IEA TCP on Solar Heating and Cooling are to overcome barriers and increase the solar global market share through research, development and testing of hardware, materials and design tools; expand the solar thermal market; and raise awareness of policy makers and consumers. There are currently 21 Contracting Parties, including China, Mexico, Singapore and South Africa, and one Sponsor.

About Technology Collaboration Programmes

The breadth and coverage of analytical expertise in the IEA Technology Collaboration Programmes (TCPs) are unique assets that underpin IEA efforts to support innovation for energy security, economic growth and environmental protection. The 38 TCPs operating today involve about 6 000 experts from government, industry and research organisations in more than 50 countries.